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Crawl Space Insulation 

Insulation in crawl spaces can be a tough decision, yet it doesn’t have to be. There is only one clear choice for insulating a crawl space, closed cell spray foam. There are a few reasons for choosing closed cell foam. Spray foam not only has insulating attributes, it has air barrier and a moisture barrier attributes for an area highly susceptible to moisture. 

Spray foam in residential crawl space
Spray foam sealing crawl space sidewalls

What areas need insulation?

In crawl spaces as well as basements, the area above the wall, called rim joist are very important to spray. They need to be sprayed and sealed with at least two inches of closed cell spray foam. This will seal any air leaks and moisture penetrations coming in through any construction joints or cracks. Spraying the rim joist alone will make a huge difference in the energy loss. 

Concrete walls, or block in most cases, are just as important to insulate as the rim joist. Concrete conducts energy very well, especially in cold weather. I can specifically relate to this. My crawl space had no insulation at all in it. Winters were frigid. I decided to call a company, before I was in business, and have my crawl space insulated. Unfortunately, they sprayed open cell in my crawl space. Although it was the wrong kind of insulation to use in a crawl space, it made a tremendous difference in my energy bill. 

Closed cell or open cell foam?

Closed cell spray foam is the only answer for crawl spaces. The purpose for this is that closed cell offers a moisture barrier attribute. Even with a plastic membrane sealed to the walls on the floor, a crawl space can still be penetrated with water through a cracked concrete wall. Closed cell will not take on moisture like open cell will.  

I personally had someone from the industry, with many more years of experience than me, try to corner me on this.  He said, “Well then what is the black tar on the exterior of the foundation for, is it not a moisture barrier?”. My response, “Yes, but concrete still cracks. Concrete settles and cracks. When concrete takes on too much moisture it cracks. Landscaping and the direction of water flow can affect and contribute to foundation problems.”. The moral of this story is look at the big picture, it’s an investment and not just another bill you’re paying.

Smooth spray foam on sdiewalls of crawlspace
Spray foam in residential crawl space

Why not use fiberglass?

Fiberglass is a great example of an air filter. Yes it will insulate some, yet it will also let it air, moisture, fine dust and mold spores. It will take on moisture if moisture is present or if the foundation leaks. Wet insulation is a health risk. 

The Value

Spray foam is a very long term investment. Unlike fiberglass, spray foam is there to stay. It will not only last for the life of your home, it will save you money on utility bills the entire time!

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